从webserver获取数据的麻烦。-Troubleingettingdatafromwebserver

I wrote this code to read and write data from webserver (mysql databse) and then all the data will be show on my andriod application.

我编写了这段代码来从webserver (mysql databse)读取和写入数据，然后所有的数据将显示在我的andriod应用程序上。

In this regard I used PHP services for reading and writing the data from web server. Everything is working fine it gets data from web server correctly but when it reaches at this line:

在这方面，我使用PHP服务来读取和写入来自web服务器的数据。一切都运行良好，它从web服务器获取数据，但当它到达这一行时:

int success = jsonObject.getInt(TAG_SUCCESS);

It shows a null pointer exception I don't know why but it actually made me insane.

它显示了一个空指针异常，我不知道为什么，但它确实让我抓狂。

Code:

代码:

        import java.util.ArrayList;
        import java.util.HashMap;
        import java.util.List;

        import org.apache.http.NameValuePair;
        import org.apache.commons.collections.*;


        //import org.json.JSONObject;

        import android.os.AsyncTask;
        import android.os.Bundle;
        import android.app.Activity;
        import android.app.ProgressDialog;
        import android.util.Log;
        import android.view.Menu;
        import android.view.View;
        import android.widget.Button;
        import android.widget.ListAdapter;
        import android.widget.ListView;
        import android.widget.SimpleAdapter;
        import org.json.*;
        public class MiddleActivity extends Activity {

            Button btnMiddleDB;

            ProgressDialog pDialog ;

            JSONParser jsOnParser= new JSONParser();

            JSONArray places = null;


            private static final String URL = "http://192.168.1.2/android_connect/get_all_products.php";

            // JSON Node names
            private static final String TAG_SUCCESS = "success";
            private static final String TAG_PRODUCTS = "products";
            private static final String TAG_PID = "pid";
            private static final String TAG_NAME = "name";

            ArrayList> placesList;



            @Override
            protected void onCreate(Bundle savedInstanceState) {
                super.onCreate(savedInstanceState);
                setContentView(R.layout.activity_middle);

                new LoadGettingFromDatabase().execute();
                btnMiddleDB = (Button) findViewById(R.id.button1);

                btnMiddleDB.setOnClickListener(new View.OnClickListener() {

                    @Override
                    public void onClick(View arg0) {


                    }
                });

            }

running background thread for getting data from webserver

运行后台线程从webserver获取数据。

            class LoadGettingFromDatabase extends AsyncTask{

                @Override
                protected void onPreExecute() {
                    super.onPreExecute();
                    pDialog = new ProgressDialog(MiddleActivity.this);
                    pDialog.setMessage("Getting from database...");
                    pDialog.setIndeterminate(false);
                    pDialog.setCancelable(true);
                    pDialog.show();
                }
        **after getting data from webserver parse it to json and store it into string**
                @Override
                protected String doInBackground(String... args) {

                    List params = new ArrayList();
                    Log.d("Seen","seen1");
                    JSONObject jsOnObject= jsonParser.makeHttpRequest(URL, "GET" ,params);
                    Log.d("String","JSON 2");

                    //Log.d("All entries","Entries" + jsonObject.toString());

                    try{
                        Log.d("Seen","seen2");

ACTUALLY THE PROBLEM IS HERE

实际上问题就在这里。

int success = jsonObject.getInt(TAG_SUCCESS);
                            Log.d("Seen","seen5");
                            if(success == 1){
                                //Entries found
                                Log.d("Seen","seen6");
                                places = jsonObject.getJSONArray(TAG_PRODUCTS);
                                for(int i=0;i hashMap = new HashMap();

                                    hashMap.put(TAG_PID, id);
                                    hashMap.put(TAG_NAME, name);

                                    placesList.add(hashMap);
                                }

                            }
                        } catch (Exception e) {
                            Log.e("success","success status " + e);
                        }       

                        return null;
                    }

                    public void onProExecute(String file_url){
                        pDialog.dismiss();
                        runOnUiThread(new Runnable(){
                            public void run(){
                                ListAdapter listAdapter = new SimpleAdapter(MiddleActivity.this, placesList, R.layout.list_item, new String[]{
                                    TAG_PID, TAG_NAME},new int[]{R.id.ID, R.id.Name});
                                ListView listView = (ListView) findViewById(R.layout.list_item);
                                listView.setAdapter(listAdapter);
                                };  
                            });
                        };
                    }

                @Override
                public boolean onCreateOptionsMenu(Menu menu) {
                    // Inflate the menu; this adds items to the action bar if it is present.
                    getMenuInflater().inflate(R.menu.activity_middle, menu);
                    return true;
                }


                }

         **and log cat is**



05-07 00:29:54.419: D/Seen(30282): seen1

        05-07 00:29:54.569: D/Seen(30282): seen3

        05-07 00:29:54.909: D/Seen(30282): seen4

        05-07 00:29:54.979: D/String(30282): JSON get_all_products.php

        05-07 00:29:54.979: D/String(30282): db_connect.php

        05-07 00:29:54.979: D/String(30282): db_config.php

        05-07 00:29:54.979: D/String(30282): {"success":0,"message":"No products found
        05-07 00:29:55.300: D/String(30282): JSON 1

        05-07 00:29:55.300: D/String(30282): JSON 2

        05-07 00:29:55.310: D/Seen(30282): seen2

    **05-07 00:29:55.310: E/success(30282): success status 

java.lang.NullPointerException**


and here is my jsonparser class
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import java.util.List;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.utils.URLEncodedUtils;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONException;
import org.json.JSONObject;

import android.util.Log;

public class JSONParser {

    static InputStream is = null;
    static JSONObject jObj = null;
    static String json = "";

    // constructor
    public JSONParser() {

    }

    // function get json from url
    // by making HTTP POST or GET method
    public JSONObject makeHttpRequest(String url, String method,
            List params) {

        // Making HTTP request
        try {

            // check for request method
            if(method == "POST"){
                // request method is POST
                // defaultHttpClient
                DefaultHttpClient httpClient = new DefaultHttpClient();
                HttpPost httpPost = new HttpPost(url);
                httpPost.setEntity(new UrlEncodedFormEntity(params));

                HttpResponse httpRespOnse= httpClient.execute(httpPost);
                HttpEntity httpEntity = httpResponse.getEntity();
                is = httpEntity.getContent();

            }else if(method == "GET"){
                // request method is GET
                DefaultHttpClient httpClient = new DefaultHttpClient();
                String paramString = URLEncodedUtils.format(params, "utf-8");
                url += "?" + paramString;
                HttpGet httpGet = new HttpGet(url);

                HttpResponse httpRespOnse= httpClient.execute(httpGet);
                HttpEntity httpEntity = httpResponse.getEntity();
                is = httpEntity.getContent();
            }           


        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        try {
            BufferedReader reader = new BufferedReader(new InputStreamReader(
                    is, "iso-8859-1"), 8);
            StringBuilder sb = new StringBuilder();
            String line = null;
            while ((line = reader.readLine()) != null) {
                sb.append(line + "\n");
            }
            is.close();
            json = sb.toString();
        } catch (Exception e) {
            Log.e("Buffer Error", "Error converting result " + e.toString());
        }

        // try parse the string to a JSON object
        try {
            jObj = new JSONObject(json);
        } catch (JSONException e) {
            Log.e("JSON Parser", "Error parsing data " + e.toString());
        }

        // return JSON String
        return jObj;

    }
}

1 个解决方案

JSONObject jsOnObject= jsonParser.makeHttpRequest(URL, "GET" ,params);